1 2 

 layers on two convex sterns and one concave stern. ' The present work is an initial 



investigation into extending to three-dimensions the previous studies on axisymmetric 



I 2 

 bodies by Huang et al. ' 



Experiments have been made to measure the flow across the thick stern boundary 

 layer of a three-dimensional body having a 3:1 elliptical transverse cross section. 

 A 10.06 ft (3.07 m) fiberglass model was tested in the Center's Anechoic Flow 

 Facility at a speed of 100 ft/sec (30.48 m/s), resulting in an overall Reynolds 

 number based on length of 6.5 x 10 . Pressure taps, embedded in the model, were 

 used to measure the pressure distribution on the surface. Velocity and turbulence 

 characteristics were measured using a two-element hot-film sensor and were analyzed 

 with an on-line computer. Measurements include mean velocity profiles, turbulence 

 intensities, Reynolds stresses, eddy viscosity, and mixing length. 



Several experimental quantities are compared with data from existing theoreti- 

 cal methods using an iterative scheme. The potential flow distribution on the body 

 surface is computed using the XYZ Potential Flow (XYZPF) computer code of Dawson and 

 Dean. An initial boundary-layer computation, using the McDonnell Douglas 

 Corporation, Cebeci, Chang, Kaups (C K) computer code, is made using the potential- 

 flow pressure distribution on the body. Flow separation is predicted for this model 



2 

 by the C K code at axial locations greater than 4 percent of the body length and 



angular locations greater than 75 degrees. Excessive boundary-layer growth in the 

 separated region caused the boundary-layer calculation to abort prematurely at 81 

 percent of the body length. Predictions of the effective displacement thickness for 

 the remaining 19 percent of the body length are obtained by extrapolation. The 

 potential and boundary-layer flow calculations are repeated once for a modified body 

 and wake geometry, formed by adding the computed effective displacement thickness. 

 Comparison of predicted and measured results shows that this procedure predicts 

 accurate values of pressure over the forward 93 percent of the body and accurate mean 

 velocity profiles in locations where the boundary layer is thin compared with cross- 

 sectional area. The measured eddy viscosity distribution is compared with the thin 

 boundary-layer model of Cebeci ' and is found to be smaller than predictions. 



In the following sections, the experimental techniques and model geometry are 

 given in detail. The experimental data are presented and compared with theoretical 

 predictions. The raw data and derived results are given in tabular form for inde- 

 pendent use by other investigators. 



